storm deck mtg commander EDH Deck Xyris, the Writhing 100 Magic Cards Custom Deck Card Draw Snakes MTG Single Cards 9 Storm Commanders for you

If enough -1/-1 counters are put on Essence Channeler at the same time to make its toughness 0 or less, its last ability will see all of the +1/+1 counters it had when it died as well as the -1/-1 counters it had, and an equal number of each of those types of counters (plus any other applicable counters) will be put onto the target creature

Karrthus is a decent example of a high-powered legend that immediately pressures life totals, but there are cheaper examples like Maarika, Brutal GladiatorMaarika, Brutal Gladiator, Kresh the BloodbraidedKresh the Bloodbraided (who starts small but can scale absurdly in the right deck), and Coram, the Undertaker (who is on paper a little fiddly but is easy enough in the format to make gigantic)

Sword of Light and Shadow can recur just with combat damage to a player

Replenish (T1, Ext, S) The life of Replenish can be measured not in years, but in weeks and months

Until end of turn, you may cast spells from among the cards in that booster pack

The key differences are background requirements and edition accuracy